<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        canvas {
            border: 1px solid #ccc;
        }
    </style>
</head>
<body>
<canvas width="600" height="400"></canvas>
<script>
    var myCanvas = document.querySelector('canvas');
    var ctx = myCanvas.getContext('2d');

    /*1.绘制两个正方形 一大200一小100 套在一起*/
    ctx.moveTo(100,100);
    ctx.lineTo(300,100);
    ctx.lineTo(300,300);
    ctx.lineTo(100,300);
    ctx.closePath();

    ctx.moveTo(150,150);
    ctx.lineTo(150,250);
    ctx.lineTo(250,250);
    ctx.lineTo(250,150);
    ctx.closePath();

    /*2.去填充*/
    //ctx.stroke();
    ctx.fillStyle = 'red';
    ctx.fill();

    /*在填充的时候回遵循非零环绕规则*/
</script>
</body>
</html>